Round Double Concave Optical Glass Lens - 2" (50mm) Diameter - 50mm Focal Length - 13mm Thick Approx. - Eisco Labs

EISCO Double Concave Lens, 50mm Focal Length, 2" (50mm) Diameter - Spherical, Optically Worked Glass Lens - Ground Edges, Polished - Great for Physics Classrooms

EISCO 6pc Optical Lens Set, 2" (50mm) Diameter - 3 Double Convex Lens & 3 Double Concave Lens - 200mm, 300mm, 500mm Focal Lengths - Optically True Glass - Ground, Beveled Edges

EISCO Double Convex Lens, 1000mm Focal Length, 3" (75mm) Diameter - Spherical, Optically Worked Glass Lens - Ground Edges, Polished - Great for Physics Classrooms